Re: Equation complexe

On 2/25/2025 1:49 PM, Chris M. Thomasson wrote:

On 2/25/2025 6:23 AM, Richard Hachel wrote:

x^4=-81
>
What is x?

  Try to forgive the floating point precision aspects, but, the roots are the r's, raising them to the 4'th power gives the p's:
_____________________
r0 = (2.12132,2.12132)
r1 = (-2.12132,2.12132)
r2 = (-2.12132,-2.12132)
r3 = (2.12132,-2.12132)
 p0 = (-81,-7.08124e-06)
p1 = (-81,-1.93183e-06)
p2 = (-81,-7.53158e-05)
p3 = (-81,4.57051e-05)
_____________________
  To gain a root, here is my code:
_____________________
ct_complex
root_calc(
     ct_complex const& z,
     int p,
     int n
) {
     float radius = std::pow(std::abs(z), 1.0 / p);
     float angle_base = std::arg(z) / p;
     float angle_step = (CT_PI * 2.0) / p;

     float angle = angle = angle_step * n;

^^^^^^^^^^^^^^^^^^^^^^
It still compiles and works wrt C++, but this looks odd to me. I typed this in the newsreader just to see if I could remember it.
That line should be:
        float angle = angle_step * n;

      ct_complex c = {
         std::cos(angle_base + angle) * radius,
         std::sin(angle_base + angle) * radius
     };
      return c;
}
_____________________
  Also, this is not using floating point for roots, just signed integers.